1. Field of the Invention
The invention relates to a method and apparatus for separating solid particles of different densities, using a magnetic process fluid.
2. Description of Related Art
Such a method is known from the Dutch patent 1 030 761. This patent describes a method and apparatus for separating solid particles in a magnetic process fluid, wherein the magnetic fluid is conducted through a magnetic field, generated by means of permanent magnets.
It should be noted that this known method and apparatus is indeed suitable for separating solid particles of greatly differing densities, wherein the density difference of the solid particles may be 1000 kg/m3 or more as for example, copper at 8900 kg/m3 in comparison with aluminum at 2700 kg/m3. Such particles are separated from each other by strong forces with the result that turbulence in the process fluid, or the possibility of clustering particles due to sedimentation, hardly influence the separation of the solid particles.
When separating solid particles such as plastic particles, seeds and diamonds of slight differences in density, in the order of up to 10 kg/3, turbulence in the process fluid or clustering of particles due to sedimentation have been shown to be very disadvantageous.
The known methods and apparatuses are not suitable for the separation of solid particles of slight differences in density, in the order of up to 10 kg/3, such as solid polypropylene and solid polyethylene particles.